Remove dependency of PrefSyncableService on PrefsTabHelper.

chrome/browser/prefs/pref_service_syncable_util.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/prefs/pref_service_syncable_util.h"
 
+#include <vector>
+
+#include "base/logging.h"
+#include "build/build_config.h"
 #include "chrome/browser/prefs/pref_service_syncable.h"
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/common/pref_names.h"
+
+#if defined(OS_ANDROID) || defined(OS_IOS)
+#include "components/proxy_config/proxy_config_pref_names.h"
+#endif
 
 PrefServiceSyncable* PrefServiceSyncableFromProfile(Profile* profile) {
   return static_cast<PrefServiceSyncable*>(profile->GetPrefs());
 }
 
 PrefServiceSyncable* PrefServiceSyncableIncognitoFromProfile(Profile* profile) {
   return static_cast<PrefServiceSyncable*>(profile->GetOffTheRecordPrefs());
 }
+
+PrefServiceSyncable* CreateIncognitoPrefServiceSyncable(
+    PrefServiceSyncable* pref_service,
+    PrefStore* incognito_extension_prefs) {
+  // List of keys that cannot be changed in the user prefs file by the incognito
+  // profile.  All preferences that store information about the browsing history
+  // or behavior of the user should have this property.
+  std::vector<const char*> overlay_pref_names;
+  overlay_pref_names.push_back(prefs::kBrowserWindowPlacement);
+  overlay_pref_names.push_back(prefs::kSaveFileDefaultDirectory);
+#if defined(OS_ANDROID) || defined(OS_IOS)
+  overlay_pref_names.push_back(proxy_config::prefs::kProxy);
+#endif
+  return pref_service->CreateIncognitoPrefService(incognito_extension_prefs,
+                                                  overlay_pref_names);
+}